Porous materials are well known. Common techniques for creating porous materials such as foams and sponges include expanding fluid, for example, by creating cells through the use of blowing agents, bubbling gas through the fluid, or mechanical agitation. However, it is difficult to form stable micro-sized pores using these methods.
In regard to membrane materials, techniques for making relatively micro-sized pores include stretching, etching, physical perforation, or mixing a base material with a soluble material and dissolving out the soluble material. However, these techniques produce poor cell uniformity and low porosity.
To produce a material with uniform micro-sized pores, it is taught in U.S. Pat. Nos. 5,451,454 and 5,716,997 that a minor amount of a high molecular weight material can be blended with a majority amount of a low molecular weight material. The low molecular weight material can subsequently be removed by an organic solvent, leaving behind a porous material of a three-dimensional continuous network cell-structure of the high molecular weight material. The cells have an average diameter of less than 500 micrometers.
These materials comprising micro-sized pores may be used in, for example, damping applications, separation applications, and adsorption applications. For instance, contaminant-free exchange of gasses may be accomplished using microporous materials. Mold spores, bacteria, and other airborne contaminants will become trapped, while allowing gasses to pass through the material. Similarly, microporous materials may be used as membranes to filter fluids, such as in water purification. However, these materials have a relatively low surface area to expose the cells (pores).
There remains a need to develop a material with a higher surface area of exposed pores to improve adsorption and separation capabilities of a porous material.